This Program Project focuses on the hypothesis that calpain inhibition represents a rationale and feasible target for therapeutic intervention following TBI. Traumatic brain injury (TBI) results in more than 50,000 deaths each year with over 5 million Americans suffering the effects of some type of TBI. In addition the need for improved therapeutics, it is important to understand the mechanisms underlying the pathological sequelae to TBI. One area that has been implicated as an important contributor to cellular injury following TBI is the calcium- and redox-dependent calpain/calpastatin proteolytic system. The central hypothesis of this core is that calpain cleavage of specific proteins is linked to cell and neuronal and dysfunction following TBI. The related hypothesis is that attenuation of this proteolysis will result in reduced degeneration and improved functional outcome. Given the strong evidence for the role of calpains in neurodegeneration, the long-term goal is to identify the targets of calpain that contribute to neurodegeneration following TBI. The goals of this Core are to: 1) provide uniform assessment of calpain substrates following TBI, including celltype specific substrates, thereby better characterizing the time-course and localization of calpain activity;2) identify and verify biomarkers of neurodegeneration to monitor injury progression as well as efficacy of therapeutics, and;3) determine the extent to which oxidative stress inhibits calpain activity over the time course of TBI, an area that remains unexplored. In collaboration with the three projects, these core studies will utilize 2D-gel electrophoresis, mass-spectrometry, Western blot analysis, and calpain activity assays with brain tissue, CSF, and serum to achieve these goals. In summary, this core will provide the needed tools and assistance for uniform analysis of calpain substrate degradation within the projects, provide additional support for the discovery of calpain substrates and related biomarkers, and provide direct measurements of calpain activity to determine the influence of oxidative stress on calpain activity following TBI.